Metal melting method and apparatus



Patented Mar. 11, 1941 UNITED STATES PATENT orrlcs METAL MELTING METHOD AND APPARATUS Application October V31, 1940, Serial No. 363,786

5 Claims.

This invention relates to the melting of metal, and more particularly to a pressure relief system for' the relief of excessive pressures caused by the non-uniform heating of frozen metal in a melting pot.

Prior to the instant invention, it has been customary to melt or remelt metal such as type metal, white metal, solder and other metals and alloys in a furnace having a pot which may be `made of cast iron or steel, which pot is heated by a heating means located therebeneath. The heating means may -be a gas heater or an electric heater. In such installations, when shutting the furnace down at the end of the days work `or for any other reason, `the molten metal within the pot will freeze into a solid mass. When the furnace is again placed in action with the heating means operative and located either beneath or in the bottom of the pot, the frozen solid mass of :metal will melt in the bottom of the pot adjacent the heater and this molten metal will tend to expand and create a dangerously excessive pressure which must find relief or crack the pot. In those pots which have bottom-pour valves, the molten metal under this excessive pressure will find its way past the valv even though the valve is tightly fitted. y It has 'been proposed that the heating be applied to the frozen mass in a more uniform man- -ner by arranging fire tubes in the melting pot at frequent intervals throughout the horizontal section thereof and extending upwardly to the top of the pot. Such prior constructions have been relatively expensive to manufacture, have P been subject to frequent damage by the striking of the fire tubes yby heavy pieces of metal to be melted, and generally must be of relatively great size to accommodate a given mass of metal because of the space occupied by the upwardly extending fire tubes.

It is an object of the instant invention to provide a novel metal melting system which will facilitate the remelting of a frozen mass of metal in la melting pot and prevent injury to the pot due to the expansion of the metal which is first melted.

It is a further object of the instant invention to provide a novel pressure relief system for the relief of excessive pressures in a melting pot which is simple in nature and foolproof.

It is another object of the instant invention to provide a melting pot with an excessive pressure relief device incorporated therein which is inexpensive to manufacture, occupies a minimum of space and is dependable.

(Cl. ESG-33) With these and other objects in view, the embodiments of the invention are described in the following specification and claims and illustrated in the accompanying drawing,lin which:

Figure l is a vertical section of -a portion of 5 a furnace including a melting pot incorporating a pressure relief system in accordance with the invention; and

Figure 2 is a view similar to Figure l but of a modified form of the invention.

Referring to Figure 1, the pot lil is supported on the walls of the furnace II directly above the gas burner I2. Formed in the pot I5 and extending from the bottom thereof to a height just above the top thereofis the muffler tube I3 15 which acts as a fire tube and serves to conduct the hot gases upwardly therethrough to the under side of the deflector III which is mounted thereon. The deflected hot gases then find their way over the top of the metal within the pot as shown by the arrows.

In order to provide a molten metal passageway from the bottom of the pot to the top thereof, the tube I5 formed with a curved portion Ilia at its lower end is Welded at It to the wall of the .rnuflier tube I3 adjacent the bottom thereof. The tube I5 is preferably of a heat resisting alloy and may be of stainless steel. The bottom Ia of the stainless steel tube I5 is arcuate in shape and extends through the wall of the muffier tube I3 for a short distance and the construction is such that the very bottom of the tube I5 is spaced about one-quarter of an inch from the bottom I1 of the melting pot Il] in order to facilitate welding.

The tube I5 may be secured adjacent its top to an opposite wall of the muler tube I3 by the collar I8, and the top of the tube I5 may be provided with a U-shaped fitting I9 for directing the metal first to be melted back into the pot.

In operation, assuming the metal within the pot I is frozen solid, and the burner I2 has just been started, the metal in the lower part of the pot I0 and the metal within the heat resisting tube I will first begin to melt, for both the bottom of they pot and the heat resisting tube I5 are more or less first directly subjected to the heating action of the hot gases emanating from the heater I2. After the metal in the bottom of the melting pot has become molten, the pressure therein may become very great unless it is relieved in some manner, and in accordance with the invention, the expanding hot metal first melted may pass upwardly through the tube I5, through the U- shaped fitting i9 and back into the melting pot, thereby relieving the pressure Within the pot and preventing injury thereto.

Should the interior of the bottom of the pot l0 be more concave than illustrated in Figure 1, the curved portion lEa of the' heat resisting tube I5 may extend through the wall of the muier tube I3 for a greater distance toward the center of the pot I0.

Referring to Figur-e 2, the pot H9 is formed with a flat bottom and supported on the furnace wall I over the burner |52 by the kettle ring |20 formed with openings |2| and |22 which occur at regular spaced intervals about the inner periphery thereof, the openings i 2| being in a horizontal plane and the openings |22 being in a vertical plane. With this construction, hot gases from the burner H2, pass across the bottom of the kettle or pot H0, upwardly along the sides thereof and then out through the openings |2| and |22 in the kettle ring. Within the path of hot gases along the side of the kettle and spaced from the side wall thereof is the relief passage means l5 communicating with the interior of the pot adjacent its bottom at |511. The passage means H5 may take the form of a tube formed at its top with a U-shaped portion H9 to conduct molten metal passing therethrough back into the melting pot 0.

In operation, the metal first melted within the melting pot is passed upwardly through the preheated relief passage ||5 which is located within the hot gas path and returned to the melting pot as shown in the drawing, thereby relieving the pressure within the pot and preventing injury thereto.

It is to be understood that it is within the scope of the invention to substitute electric heaters for the burners l2 and ||2 and also to 40 locate the heaters directly within the melting pot when desired. Should the heaters be located directly within the melting pot, the relief passages provided by the conduits l5 and 5 should have their lower portion extending into the melting pot to a point adjacent the heating means. While the muffler tube I3 in Figure 1 is located to one side of the center of the pot IU, it is to be understood that it may be more centrally, or centrally, 1ocated without departing from the spirit of the invention.

It will be obvious to those skilled in the art that various changes may be made in this device Without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawing and described in the specication but only as indicated in the appended claims.

What is claimed is:

1. The method of melting a mass of solid frozen metal in a melting pot"corn1;irisingl applying heat to a portion of the pot to first melt a rst part of the metal therein, heating a molten metal passage leading from said first melted metal part and in non-heat conducting relation with the unmelted second part of the metal, whereby the first melted part may expand and be relieved, and passing said rst melted expanded part into direct contact with the exterior of the second unmelted part.

2. A metal melting furnace comprising a metal melting pot, heating means associated therewith to melt the metal therein, hot gas passage means leading from said heating means, molten metal relief passage means leading from within said melting pot adjacent the place rst receiving heat from said heating means and extending through said hot gas passage means and back toward and in discharging relation to the interior of, saidA pot.

3. The structure recited in claim 2, said heat resisting conduit being formed of stainless steel.

4. A metal melting furnace comprising a melting pot, heating means therefor, a fire tube extending upwardly and in heat exchange relation with said pot, a relief conduit extending through said nre tube with the bottom thereof adjacent the bottom of said pot, said heating means being located directly below said pot whereby the metal first to be melted may be passed upwardly through said relief conduit.

5. A metal melting furnace comprising a melting pot,.a heating means disposed therebelow and a hot gas passage extending up one side of said pot, a relief conduit leading from the interior of the bottom of said pot and extending upwardly through said hot gas passage and back toward and in discharging relation to the interior of said pot.

HENRY HARTMANN. 

